Lesson 5 Assumption vs. Justify Questions

[uchong]

I am having trouble differentiating between Assumption and Justify questions.

I understand that Assumption questions look for what is necessary and Justify questions look for what is sufficient. But is it possible for one stimulus and answer pair to be BOTH an Assumption and Justify type of question? For example, in the Lesson 5 On-Demand video, a simple example Supporter Assumption stimulus is discussed:

All humans are mortal. Therefore, Socrates is mortal.

The Assumption question stem would be something like The argument assumes which one of the following or What would the author have to assume for the conclusion to be true and clearly the answer is something like:

Socrates is human.

But couldn't the exact same stimulus and answer pair be used for a Justify question? With the exact same stimulus and the exact same answer, couldn't a question stem be Which of the following justifies the conclusion? In this case, Socrates is human would still be a correct answer for this question.

Both stimuli and answer pairs are identical, but the question stem can be phrased as either an Assumption or Justify type of question. If this is correct, then why are the methods for solving these two types of questions different?

[Jeremy Press]

Hi uchong,

What you're noticing, which is true, is that sometimes an assumption is both necessary and sufficient for a particular argument, and therefore could provide the answer to an Assumption or a Justify question. The example you mention is one of those. However, there are only a narrow range of assumptions that fit that category. Consistent with the example you mentioned, most of those Assumptions fill a Supporter role (closing an obvious gap between the premise and the conclusion).

Many (probably most) other assumptions fill either a necessary (Assumption question) role, or a sufficient (Justify question) role, but not both.

Consider an example I use with my classes. Let's say I'm trying to argue that you passed the Illinois bar exam (my conclusion is: You passed the Illinois bar exam). A little background for you: to pass the Illinois bar you need to score 266 out of 400 available points, and 50% of the test is multiple choice, 30% is essay, and 20% is a performance test that consists of a short practical "legal project."

Assumptions that are Necessary, but NOT Sufficient - Correct Answers to an Assumption Question
--You can read
--You can write
--You studied at least a little bit
--You registered to take the test in Illinois

Assumptions that are Sufficient, but NOT Necessary - Correct Answers to a Justify Question
--You got a perfect score on the exam.
--You got the highest score of anyone in the state in a test administration for which many people passed the exam.
--You scored 300 points on the exam.

Assumption that is both Sufficient AND Necessary - Correct Answer to a Justify AND an Assumption Question
--You got 266 points on the exam.

Far more of our Justify and Assumption questions use answers drawn from those first two categories. But occasionally you get a question (like the Socrates one) that fits into the last category. Don't let that throw you off, and don't let that make you think about the question types any differently. An Assumption question asks for an answer choice that is strictly necessary for the argument and its conclusion. A Justify question asks for an answer choice that is sufficient to prove, or validate, the argument and its conclusion.

I hope this helps!

[uchong]

Thanks Jeremy! Very helpful.